Juveniles live in nursery bays and migrate to sandy areas along the coast as they grow. Males mature faster than females, and leave nursery areas for the open coast at 2 to 3 years of age and 20 to 23 cm in length, while females migrate as slightly larger sub-adults, at a length of around 25 cm. (Haugen, 1990)

Physical Description

California halibut are large, oval-shaped flatfish, with a symmetrical mouth and sharp, canine-like teeth. They have long gill rakers and relatively small eyes. Olfactory rosettes and cephalic lateralis pores are found on their snout and jaw, respectively. At the beginning of the larval stage, one eye is on each side of the head. As individuals mature into the postlarval stage (at 20 to 29 days), one of the eyes migrates to the other side, leaving the animal with 2 eyes on the 'dorsal' side (which technically is still its lateral side). The body is firm, with paired pectoral fins and a wide caudal fin, which is used for rapid propulsion. Coloration is normally brown to brownish-black on the dorsum, and white on the ventral side. The chromatophores in the skin are capable of changing the animal's color and patterning to match its environment. The lateral line is arched above the pectoral fin. California halibut reach a maximum size of 152 cm and a mass of 33 kg. ("California Halibut Identification", 2012; Haugen, 1990)

California halibut may be confused with Pacific halibut (Hippoglossus stenolepis). These two species can be distinguished by the length of the maxilla, which reaches beyond the eye in California halibut (versus just reaching the front edge of the eye in Pacific halibut), and the number of dorsal fin rays, which is always less than 77 in California halibut (versus 80 or more in Pacific halibut). ("California Halibut Identification", 2012)

Development

Larvae hatch at about 2 mm in length, and undergo a change in form 20 to 29 days post-hatching, after which they settle to the bottom of bays when the larvae attain sizes between 7.5 to 9.4 mm. Paralichthys californicus is unique in that 20 to 29 days after its larval stage, one of its eyes migrates to the same side as the other eye. It can either be dextral or sinistral, meaning that both the eyes may be located on the right or left side of its head. ("California Halibut Identification", 2012; Haugen, 1990)

Males become sexually mature at 2 to 3 years of age and a standard length of 20 to 23 cm. Females mature later, at 4 to 5 years and 38 to 43 cm in standard length. Spawning season occurs from February to August, most commonly taking place in May. California halibut eggs are 0.7 to 0.8 mm in size and are mainly found close to the shore, in shallow water between 12 and 45 m. ("California Halibut", 2012a; Haugen, 1990)

Spawning may occur from February to August, but most commonly happens in May.

Average number of offspring

420,000 eggs

Range age at sexual or reproductive maturity (female)

4 to 5 years

Range age at sexual or reproductive maturity (male)

2 to 3 years

There is no parental investment, as this species is a broadcast spawner with planktonic larvae. (Haugen, 1990)

Parental Investment

no parental involvement

Lifespan/Longevity

California halibut live for up to 30 years in the wild. A study has shown that California halibut are generally older in Southern California, as opposed to Central California. Little is known about their longevity in captivity. (MacNair, et al., 2001)

Range lifespanStatus: wild

30 (high) years

Behavior

California halibut are solitary ambush predators that lie on the bottom, waiting for their prey to swim by. They use chromatophores to help match the color and patterning of the sand and muddy flats which they inhabit, which allows them to be inconspicuous to their prey. Contrary to popular belief, they can be rather active, as they have been seen swimming in anchovy schools and chasing the fish up to the ocean surface, sometimes even leaping out of the water to catch them. ("California Halibut", 2012b; Haugen, 1990)

Home Range

Tagging studies indicate that nearly half of tagged adults displayed no net movement from their point of release, and half moved no more than 1 km after one year. (Tupen, 1990)

Communication and Perception

Communication in California halibut has not been extensively studied or observed. They are able to use their lateral line to detect vibrations in the water, aiding in prey location and predator avoidance. Because one of the eyes migrates to the other side of the head, and because the eyes are sensitive to patterns, they are able to lay flat on the bottom of the ocean, camouflaging themselves and enabling them to better spot their prey. This species is also able to sense chemical cues in the water, using the olfactory rosettes found in its nares. ("California Halibut", 2012b; Haugen, 1990; Karleskint, et al., 2010)

Food Habits

California halibut are carnivorous, with their diet changing in association with growth. They feed both during the day and night, but appear to favor catching prey during the day. Juveniles (less than 55 mm) feed mainly on small crustaceans, such as harpacticoid copepods, small gammarid amphipods, and mysid shrimps. As they grow to 55 to 230 mm, they feed on shrimp and small fishes, such as gobies, topsmelt (Atherinops affinis), and California killifish (Fundulus parvipinnis). As juveniles grow and migrate out of protected bays, their diet switches yet again, to larger, faster-swimming prey. Young adult and mature California halibut are known to feed on northern anchovies (Engraulis mordax) and mysids. (Haugen, 1990; Wertz and Domeier, 1997)

Halibut partially or completely bury themselves in the sand (leaving the eyes exposed) to hide from their prey. They wait and watch the prey item until it is less than three head lengths away, and then strike with a swift upward lunging motion, snatching it. If the strike fails, they will chase the prey until it is captured. (Haugen, 1990; Wertz and Domeier, 1997)

Predation

Juvenile California halibut may be preyed upon by shorebirds, waterfowl, and larger fishes while they reside in shallow bays. Adult California halibut in coastal regions are fed on by Pacific angel sharks, Pacific electric rays, California sea lions, and bottlenose dolphins. In some cases, larger halibut are known to feed on their smaller counterparts. (Haugen, 1990)

In order to avoid predators, California halibut bury themselves in the sand and use their camouflage abilities to blend in with the sea bottom. Due to their well-developed swimming abilities, they are also able to escape from some of their predators even if they are detected. (Haugen, 1990)

Ecosystem Roles

California halibut play a crucial role in the neritic food chain, as they are a vital source of food for predators, in addition to being secondary and tertiary consumers themselves. (Haugen, 1990)

Mutualism and commensalism between this species and others has not been observed, but it is known to host a number of endo- and ectoparasites. Known endoparasites include flukes, tapeworms, and nematodes, which infest the intestinal tract. Ectoparasites include copepods and isopods, which attach themselves to the gills and scales. (Allen, 1990)

Economic Importance for Humans: Positive

California halibut are widely sold and consumed by humans. The species has supported recreational and commercial fisheries throughout the west coast of North America since the early twentieth century. According to the Department of Fish and Game, 239,558 kg of California halibut were landed in 2010. The total value, computed from prices paid to fishermen, was estimated at $2,347,179. ("Final 2010 California Commercial Landings", 2011; Haugen, 1990)

Economic Importance for Humans: Negative

California halibut have not been known to cause any significant problems or harm to humans. However, they have very sharp teeth and will potentially bite, if handled. ("California Halibut", 2012b)

Negative Impacts

injures humans

bites or stings

Conservation Status

In 2011, the California Department of Fish and Game completed its first stock assessment of the California halibut population in Southern California. An independent panel review found numerous problems with inadequate sampling and other deficiencies in the data provided by this assessment, but nonetheless found that the population was depleted to about 14% of its unexploited level, and noted that recruitment had declined sharply since 1999. However, no conservation initiatives have yet been enacted for this species. (Maunder, 2011)

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

acoustic

uses sound to communicate

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal

active during the day, 2. lasting for one day.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

planktivore

an animal that mainly eats plankton

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

Disclaimer:
The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.